US2992218A - Nu, nu'-bis cyanoethyl styrene-bis-benzimidazole brighteners - Google Patents

Description

or brighteners.

This invention relates to new optical bleaching agents More specifically, this invention relates to compounds of the formula l CH2 in which R and R are hydrogen, lower alkyl, chlorine or bromine.

Optical bleaching agents have been developed for a wide variety of fibers. A large number of different classes of compounds have been and are being produced for this purpose. With the introduction of each new synthetic fiber, new problems of application for obtaining satisfactory brightening have been encountered and new brightening agents have had to be developed.

A further complication to the problem of brightening textile fibers has been the increased prevalence of various resin treatments for the textile fibers, especially cellulose fibers. Resins are applied to cellulosic fabrics to increase wrinkle resistance and crease resistance and to achieve many other improved properties. While these resins give the consumer greatly improved textiles, they present great problems in the optical bleaching field. The brighteners in present use do not effectively brighten resin-treated cotton. The most commonly used ones, such as those derived from stilbenedisulfonic acid, which have excellent aflinity for untreated cotton, have much impaired affinity for resin-treated cotton as shown by poor exhaustion and poor fasteness to rinsing.

A restricted class of optical bleaching agents based on the styrene bis-benzirnidazole ring structure has recently been developed which shows good aifinity for resintreated cotton. This has been a very important development in this field, opening as it does the possibility of properly brightening the many resin-treated fabrics which are used today. However, the compounds which have been described in this class of styrene-bis-benzimidazole brightener have had one serious deficiency they tend to turn yellow whenexposed to acid. This is a very embarrassing property since it causes staining of fabrics when they are exposed to acid perspiration. Such discoloration can also occur when the clothes are exposed to an acid atmosphere. Since the many exhaust gases from the machines of modern civilization pollute the atmosphere of todays cities with acidic materials, this discoloration can also become quite general on such fabrics. A further incidence of such discoloration can occur when the fabrics are subjected to an acid sour commercial laundering.

cyanoethylamino) aniline.

Patented July 11, 1961 We have found that compounds of the formula H; CH2

in which R and R are hydrogen, lower alkyl, chlorine or bromine are also excellent brighteners for resin-treated cotton. In addition, they exhibit stability to acid conditions which makes them free of the yellow staining which is the serious deficiency of these brighteners heretofore known. It will be observed that the principal difierence between these compounds and the compounds heretofore known of this general structure lies in the substituent on the imidazole nitrogen. In the compounds of our invention, this substituent is Z-cyanoethyl. In general, because of the simplicity of the preparation, it is preferred that R and R be hydrogen, i.e., that the styrene bisbenzimidazole nucleons be unsubstituted except for the cyanoethyl groups on the imidazole nitrogens. It is however possible and within the scope of our invention to have such groups as methyl, ethyl, butyl, amyl, chlorine or bromine on the benzimidazole carbocyclic rings in the structure, as illustrated in the above formula and in the examples below.

The brighteners of our invention are conveniently prepared by the reaction of p-carboxycinnamic acid with an o-phenylenediamine followed by ring closure to the bisirnidazole. p-Carboxycinnamic acid is obtainable by a number of alternative routes. For example, terephthalaldehydic ester may be converted to p-carboxycinnamic acid by reaction with acetic anhydride in the presence of sodium acetate. The compound may also be prepared from terephthalaldehydic ester with malonic acid followed by decarboxylation. A further preparation is a Meerwein type of condensation reaction in which a diazotized p-aminobenzoic acid is condensed with maleic anhydride; decarboxylation occurs spontaneously to give the desired p-carboxycinnamic acid.

The o-phenylenediamines with which the p-carboxycinnamic acids are condensed to form the compounds of my invention include the following:

o-Phenylenediamine 4-methyl-1,2-phenylenediamine S-methyl-1,2-phenylenediamine 4-ethyl-1,2-phenylenediamine 4-propy-l-1,2-phenylenediamine 3-chloro-1,2-phenylenediamine 4-chloro-1,2-phenylenediamine 4-bromo-1,2-phenylenediamine The cyanoethyl substituent on the imidazole nitrogen can be introduced to the molecule by starting with 2-(2- It is, however, much preferable to introduce the cyanoethyl group after synthesis of p the styrene bis-benzimidazole ring structure. This is done by the alkylation of the styrene bis-benzimidazole with acrylonitrile. The alkylation is ordinarily carried out by condensation of acrylonitrile with the benzimidazole starting compound in the presence of a basic catalyst. Tetramethylguanidine is suitable as a catalyst for this purpose since it is a strong base soluble in the organic media generally preferred for the reaction. It is convenient to use liquid acrylonitrile as the solvent for the reaction. Alternatively, however, such materials as ethoxyethanol are convenient as reaction vehicles. Alternatively to al-kylation by acrylonitrile, one can alkylate by reaction with a halogen compound such as beta-chloropropio-nitrile to get the same alkylation product.

The brighteners of our invention may be applied by the usual methods for applying non-ionic brighteners. A useful method is dissolution of the brightener in a solvent, such as dimethylformamide, and the addition of the solvent solution to water, or to water containing a surfaceaotive agent, to form a dispersion. This dispersion is then used as a dye bath from which the brightener can be applied to the fabric.

The products of our invention are especially useful for application to resin-treated cellulosic fabrics, especially cotton fabrics. Cot-ton fabrics of this type are often treated with such resins as polymethylolalted melamine, dimet-hylolurea, substituted alkylene ureas, rtriazones, such as dirnethyloltetrahydro-S-ethyl-2(1)-triazone, diglycidyl others, and alkylated derivatives of these materials. One or more of these represent the standard textile resin treatments of cellulose.

Our invention can be illustrated by the following examples in which parts are by weight unless otherwise specified and in which parts by volume are to parts by weight as milliliters are to grams.

Example 1 A mixture of 5.66 parts of the ethyl ester of terephthal aldehydic acid and 3.64 parts of malonic acid in 9 parts t 95% ethanol containing 1 part of pyridine is heated at the reflux temperature until reaction is substantially complete. The solvent is then removed from the mixture by evaporation. To the residue is added 9 pants 95% ethanol and parts of 5 N sodium hydroxide solution. The resulting slurry is heated a short time at steam bath temperature (to hydrolyze the ester group) and the mixture is then diluted to about 200 parts total with water. After clarification and acidification with concentrated hydrochloric acid the solid product is removed by filtration, washed with hot water and dried.

Example 2 p-Aminobenzoic acid is diazotized by dissolving 137 g. in a mixture of 680 ml. of water and 183 ml. of cone. H01, and adding a solution of 69 g. of sodium nitrite in 180 ml. water at 0 C. Sulfamic acid is added to destroy excess nitrous acid, followed by 330 g. of sodium acetate trihydr-ate to lower the acidity. This diazo solution, at room temperature, is now added to a solution of 108 g. of maleic anhydride in 2500 ml. of acetone followed by a solution of 42 g. of cupric chloride in 200 ml. of water. The reaction is exothermic, and the temperature rises to 35-40 C. It is allowed to proceed to completion without temperature control, and when the evolution of nitro gen has ceased and there is no further evidence of diazo present, the mixture is heated briefly at 50 C. and strong- 1y acidified. After removal of the acetone, (the precipitate is filtered off and washed. This gives crude trans-p-carboxycinnamic acid. Chilling of the mother liquor gives additional yield of crude p-carboxycinnarnic acid, this being the cis isomer. Either the cis or trans isomer or a mixture of the two can be used without purification in the next step for preparing bis-benzimidazole brighteners, the same product being obtained in any case.

A mixture of 1.92 parts of p-carboxycinnamic acid, from Example 1, 12. parts of o-phenylenediamine and 0.1 part of boric acid is heated with stirring at 200-205 C. :for a short time and then at 240 C. until reaction is substantially complete. After cooling, 45 parts of ethanol is added. After agitation, the solid product is removed by filitration. The solid is ground and extracted with 95% ethanol. After extraction, the residue is dissolved in 270 parts 95 ethanol and 20 parts 5 -N sodium hydroxide at the boiling point. After clarification with activated charcoal, the solution is diluted with 600 parts water and acidified with concentrated hydrochloric acid. The solid product which precipitates is removed by filtration and dried giving 2.18 parts of the desired brightener compound. This may be purified by further reprecipitation from alkaline solution by acidification.

Example 4 /N N n H as o-on=on-o C a A mixture of 19.2 parts of p-carboxycinnamic acid and 12 parts of 4-methy1-1,Z-phenylenediamine is reacted according to the procedure of Example 3, giving the corresponding nuclear-substituted bis-benzimidazole. If, instead of 4-methyl-1,2-phenylenediamine, there is used an equimolar amount of 4-chloro-1,2-phenylenediamine or 4-bromo1,Z-phenylenediamine, one obtains the correspondingly substituted bis-benzimidazole.

A mixture of 15.7 parts of the styrene-bis-benzimidazole prepared in Example 3, 200 parts by volume of acrylonitrile, and 20 parts by volume of tetramethylguanidine is heated, with stirring, until substantial completion of the reaction. The solid product which forms is isolated by filtration and dried. It may be purified by dissolving in 400 parts by volume of methoxyethanol clarifying and reprecipitating the product by the addition of an equal volume of Water. The product may then be isolated by filtration.

When any of the substituted styrene-bis-benzimidazoles described in Example 4 is used in equivalent quantity in place of the unsubstituted compound in the above procedure, the correspondingly substituted product is obtained.

Example 6 One hundred milligrams of the brightener of Example 5 is dissolved in m1. of dimethylformamide at room temperature. The solution is diluted to 200 ml. with dimethylformamide. Fifty milliliters of this clear 0.05% solution is then added to 40 ml. of water containing 10 g. of Deceresol NI come. (a non-ionic surfactant of the phenol polyoxyethylene ester type). The resulting sus- 5 6 pension is diluted to 500 ml. with water, giving a 0.005% in which R and R are each selected from the group consuspension. sisting of hydrogen, lower alkyl, chlorine and bromine.

This suspension is then used as the dye bath in the 2. The compound dyeing of cotton modified with 5% of a polymethoxy- N methylaminotriazine compound. The dye bath is heated 6 bright white appearance in contrast to the dull yellowish appearance of the same cotton before laundering with N at 130 F. while the cloth is agitated therein. The cloth is then rinsed in hot water and dried. It has a pleasing brightener. The resin-treated cotton thus dyed shows 10 little or no discoloration when exposed to acetic acid H1 H1 fumes, nor is the fluorescence diminished appreciably. N N

We claim: 1. A compound of the formula References Cited in the file of this patent 15 UNITED STATES PATENTS R, I \C-CH=CH-C R, 2,463,246 Graenacher et a1 Mar. 1, 1949 2,838,504 Crounse June 10, 1958 N N I 3 20 FOREIGN PATENTS I I g i 1,172,134 France Oct. 13, 1958 {IN N

Claims (1)

1. A COMPOUND OF THE FORMULA